Vial of Inexplicably Heavy Water

 is an item in Bastard's Wound.

Description
This vial of crystal-clear water is much heavier than a vial of plain water has any right to be.

Location

 * Obtained from Wagstaff as reward for Blood of the Beast (or if you ask him 'what will you give me if i do this' before taking the quest), if you kill him during Fatebinder's Judgement, or if you trade with Cassandra's Gravelight tools.
 * Used to craft Wave's Crest.